1. Field of the Invention
The present invention relates to an internal combustion engine which is cooled by a so-called boiling liquid cooling system, and more particularly to an improved cylinder block for such engine wherein coolant is introduced thereinto in a liquid state and exhausted therefrom to a heat exchanger in a gaseous state.
2. Description of the Prior Art
Hitherto, there has been proposed a so-called boiling liquid cooling system (viz., evaporative cooling system) for cooling an internal combustion engine. This type cooling system basically features an arrangement wherein a liquid coolant (water) in the coolant jacket of the engine is permitted to boil and the gaseous coolant thus produced is passed out to an air-cooled heat exchanger or condenser where the gaseous coolant is cooled or liquefied and then recirculated back into the coolant jacket of the engine. Due to the effective heat exchange effected between the gaseous coolant in the condenser and the atomosphere surrounding the condenser, the cooling system exhibits a very high performance. Japanese Patent Application Second Publication Sho No. 57-57608 and Japanese Patent Application Sho No. 58-86632 show some examples of the above-mentioned cooling systems. Furthermore, copending U.S. patent application No. 602,451 filed on Apr. 20, 1984 in the name of Yoshimasa Hayashi shows another example of such cooling system.
However, as will become apparent as the description proceeds, the previously proposed systems are constructed without paying any regard to reduction in engine noise. That is to say, the internal combustion engines equipped with such type cooling system have inevitably produced a considerable engine noise due to a non-rigid construction of the cylinder block of the engine proper.